Hydrogenation catalyst



HYDROGENATION CATALYST Robert L. Hadley, Louisville, Ky., assignor to General Electric Company, a corporation of New York No Drawing. Filed Dec. 13, 1955, Ser. No. 552,708

4 Claims. (Cl. 252-470) This invention relates to new catalysts which contain molybdenum and nickel. More particularly, this invention relates to finely divided porous catalysts comprising an alloy of molybdenum and nickel in porous, activated form with molybdenum being present in an amount equal to up to 12 and preferably from about 2.0 to 8.0 percent by weight based on the total weight of the catalyst with the remainder of the catalyst being substantially all nickel. These catalysts are prepared by treating powdered nickel-aluminum-molybdenum alloys in a strong alkaline solution whereby the aluminum is removed from the alloy particles leaving as the residue porous particles of nickelmolybdenum which are similar to Raney nickel.

Raney nickel is a well known hydrogenation catalyst and is described in Patent 1,628,190, Raney, and in J.A.C.S. S4, 4116 (1932). Raney nickel is generally prepared from an alloy containing from to 85 percent nickel and from 90 to 15 percent aluminum. This alloy is pulverized and treated with aqueous sodium hydroxide or other suitable strong aqueous alkalis to leach the aluminium from the alloy. This results in a finely divided porous, activated nickel catalyst. Instead of preparing the catalyst from a binary alloy of nickel and aluminum, Raney nickel may also be prepared from a nickel-base alloy in which some or all of the aluminum is replaced by silicon.

Although Raney nickel is a suitable catalyst for many hydrogenation reactions, its activity is sometimes not as high as desired. It has previously been found that for certain hydrogenation reactions a Raney-type nickel catalyst containing a small amount of chromium had greater activity than Raney nickel. These chromium-nickel catalysts have contained from about 0.5 to 3.5 percent chromium, balance substantially all nickel and have been prepared by treating an appropriate powdered nickelaluminum-chromium alloy in a strong alkaline solution whereby the aluminum is removed from the alloy particles leaving as a residue porous particles of nickelchromium similar to Raney nickel.

Unfortunately, these nickel-chromium catalysts have not been found to be uniformly reproducible. Under substantially identical reaction conditions involving identical hydrogenation reactions, different batches of nickelchromium catalysts prepared under identical leaching conditions from pulverized nickel-aluminum-chromium alloys having substantially identical compositions have been found to have substantially different activities. Further, such substantially identical nickel-aluminum-chromium alloys have been found to have varying degrees of stability. For example, it has been found that certain batches of these alloys tend to lose part of their chromium content at an undesirably greater rate than other batches during the leaching step of the catalyst preparation. This results in an undesirable and uncontrollable variation in composition of the catalysts. Further, prepared nickel-chromium catalysts are undesirably unstable under conventional storage conditions. Raney nickel catalysts and the nickel-chromium catalysts are pyro phoric and must be protected from the atmosphere during storage and use. Raney nickel catalysts may be successfully stored under water for considerable periods of time without excessive deterioration. The nickelchromium catalysts, however, deteriorate at a substantially greater rate under water and require more expensive storage techniques if excessive deterioration is to be avoided.

The present invention is based upon my discovery that nickel-aluminum-molybdenum alloys of appropriate compositions may be treated to provide nickel-molybdenum hydrogenation catalysts which have a significantly greater activity than Raney nickel in the hydrogenation of certain carbonyl compounds and in certain systems where Raney-type catalysts are otherwise poisoned. Furthermore, they have a regularly reproducible activity which is equivalent to the better nickel-chromium catalysts. Further, these nickel-molybdenum catalysts are chemically stable during the leaching step in that little, if any molybdenum is lost during the preparation and the catalysts may be easily and readily stored under water for long periods of time Without excessive loss of activity.

In preparing catalysts of the present invention, a ternary alloy consisting essentially of aluminum, nickel and molybdenum is prepared by any conventional alloying procedure such as by melting a charge consisting of a quantity of nickel, an amount of molybdenum equal to 12.0 percent by weight of the nickel and a sufiicient amount of aluminum to constitute 40 to 60 percent by Weight of the total charge. Specifically, I prefer to melt a charge consisting of about 50 weight percent aluminum, 0.25 to 6 weight percent molybdenum, and the balance nickel in an inert atmosphere furnace. The metals comprising the alloy may be melted by any convenient means such as electrical induction heating, are melting or the like, and the melt may be agitated to promote distribution of the constituent metals if desired. The molten alloy may be tapped from the furnace crucible into molds if desired, or the molten alloy may be permitted to solidify in the furnace crucible from which it may be removed when cool.

The resulting alloy is quite brittle and may be readily broken up or pulverized. I prefer that the alloy be reduced to about mesh powder or finer although this particular particle size is not critical and may vary there from within quite substantial limits.

The powdered alloy is then digested in a strong alkaline solution such as an aqueous caustic soda solution in accordance with known procedures for attacking nickelaluminum alloys. After the aluminum has been substantially removed by this digestion or leaching process, the residue comprises the nickel-molybdenum catalyst of my invention. During the leaching process there is no evidence that any substantial amount of molybdenum is lost from the alloy. As pointed out previously, the catalysts of the present invention contain up to 12 percent by weight of molybdenum based on the total weight of the finished catalyst.

In evaluating a new hydrogenation catalyst it is necessary to compare the efiiciency of the new catalyst with the efficiency of a known catalyst under a standard set of conditions. For purposes of the present disclosure the nickel-molybdenum catalysts were compared to commerical Raney nickel and nickel-chromium catalysts in the hydrogenation of a given amount of glucose to sorbitol at a given temperature with a given hydrogen pressure and With a given amount of catalyst under given conditions of agitation. The reaction rate observed with the catalysts of the present invention was then compared with the reaction rates observed with Raney nickel and with nickel-chromium catalysts.

'It has been found that the reaction which comprises the hydrogenation of glucose to sorbitol is a pseudofirst order reaction and, therefore, at a given hydrogen pressure and at a given temperature, the rate of reaction is directly proportional to theconcentration of the material being hydrogenated. in equation form this may be expressed as where C is the concentration of glucose, t is time, and k is a constant. Upon integration of Equation 1 from time 0 to time t, it has been found that the logarithm of the initial concentration over the concentration at time t is proportional to the time of the reaction as expressed by the following equation (2) log -Kt I where C is the concentration of glucose at time t, C is the initial concentration of glucose and K is a proportionality constant. i

In following the hydrogenation reactions employing catalysts of the present invention, Raney nickel or nickel-chromium catalysts, the change in concentration of glucose with time was followed by measuring the amount of hydrogen used in the reaction with time. The log of the initial concentration of glucose divided by the glucose concentration at time t was plotted against time. For convenience, one thousand times the slope of the resulting straight line was taken at the rate constant in the present application.

The following examples are for purposes of illustration only and are not intended as a limitation on the scope of the present invention.

In each of the following examples a different catalyst was used in the hydrogenation of 45 grams of glucose in 135 grams of the monomethyl ether of ethylene glycol (methyl Cellosolve). The catalyst was added to this reaction mixture and the hydrogenation was then run at a temperature of 125 C. and a hydrogen pressure of about 50 p.s.i.g. under standardized conditions of agitation. The total amount of hydrogen consumed at various stages of the reaction was observed and from this data the rate constant was calculated.

Four different nickel-molybdenum catalysts were pre pared from four 'difierent nickel-aluminu1n-molybdenum alloys which had been prepared by melting the constituent metals as previously disclosed. In each of the following Examples 1 to '4, the nickel-molybdenum catalyst recited in each case had been prepared from the corresponding nickel-aluminum-molybdenum alloy in the following manner. Forty-five grams of the alloy, ground to all pass 80 mesh, was added with stirring and external ice cooling to a solution of 45 grams of commercial analytical reagent grade sodium hydroxide pellets in 180 ml. of distilled water at such a rate that the temperature did not exceed 50 C. The resulting foaming slurry was then boiled gently at 110 to 115 C. for three hours. A second lot of 45 grams of analytical reagent grade sodium hydroxide pellets dissolved in 180 ml. of distilled water was added to the gently boiling slurry at such a rate that boiling was not interrupted and the boiling was continued for an additional three hours. During the entire digestion period the boiling temperature was controlled by the addition of distilled water as needed to replace that lost by evaporation. When the digestion period was completed the finely divided catalyst was allowed to cool and settle and the supernatant solution was removed by decantation, The catalyst was then washed in a stream of distilled water in a suitable vertical washing tube until it was substantially tree of alkali as measured by a pH meter. 7

The Raney nickel described in Example 5 is commercial Raney nickel which is prepared by leaching the aluminum from a finely divided alloy of equal parts by weight of aluminum and nickel with the leaching solution being a sodium hydroxide solution, generally a 20 percent sodium hydroxide solution.

Three different nickel-chromium catalysts were pre pared from three different nickel-aluminum-chromium alloys which had been prepared by melting the constituent metals in the same manner as previously described for the nickel-aluminum-molybdenum catalysts. Further, the same grinding, leaching and Washing procedure disclosed in connection with the preparation of the nickelmolybdenum catalysts was followed in the preparation of the nickel-chromium catalysts used in the reactions of Examples 6 to 8.

Example 1 Example 2 An alloy comprising about 2.5 percent by weight molybdenum, 47.5 percent by Weight nickel and 50 percent by weight aluminum was pulversized to pass an 80 mesh screen. Forty-five grams of this pulverized alloy was digested in sodium hydroxide as described previously. About 3.0 grams of the washed catalyst was then evaluated by the method described previously. This hydrogenation proceeded with the rate constant of 24.0. The nickel-molybdenum catalyst employed contained about 5 weight percentof molybdenum based on the total weight of the catalyst.

Example 3 An alloy comprising about 1.0 percent by weight molybdenum, 49.0 percent by weight nickel and 50 percent by Weight aluminum was pulverized to pass an mesh screen. Forty-five grams of this pulverized alloy was digested in sodium hydroxide as described previously. About 3.0 grams of the washed catalyst was then evaluated by the method described previously. This hydrogenation proceeded with a rate constant of 16.8. The nickelmolybdenum catalyst employed contained about 2 weight percent of molybdenum based on the total weight of the catalyst.

Example 4 An alloy comprising about 0.5 percent by weight molybdenum, 49.5 percent by weight nickel and 50 percent by weight aluminum was pulverized to pass an 80 mesh screen. Forty-five grams of this pulverized alloy was digested in sodium hydroxide as described previously. About 3.0 grams of the washed catalyst was then evaluated by the method described previously. This hydrogenation proceeded with a rate constant of 15.4. The nickel-molybdenum catalyst employed contained about 1 weight percent of molybdenum based on the total weight of the catalyst.

Example 5 This example describes a hydrogenation employing the reaction mixture described previously and employing commercial Raney'nickel. About 3.0 grams of commercial Raney nickel were added to the reaction mixture described previously and during the hydrogenation the reaction rate observed was only 4.5. From this example it is obvious that the catalysts of the present invention are more than three times as efiective as commercial Raney nickel in these hydrogenation reactions.

Example 6 Example 7 An alloy comprising about 1.0 percent by weight chromium, 49.0 percent by weight nickel and 50.0 percent by weight aluminum was pulverized to pass an 80 mesh screen. Forty-five grams of this alloy was digested in sodium hydroxide as described previously. About 3.0 grams of the washed catalyst was evaluated by the method described previously. This hydrogenation proceeded with a rate constant of 18.2. The nickel-chromium catalyst employed contained about 2 weight percent chromium based on the total weight of the catalyst.

Example 8 An alloy comprising about 0.5 weight percent chromium, 49.5 weight percent nickel and 50.0 weight percent aluminum was pulverized to pass an 80 mesh screen. Forty-five grams of this alloy was digested in sodium hydroxide as described previously. About 3.0 grams of the washed catalyst was evaluated by the method described previously. This hydrogenation proceeded with a rate constant of 17.9. The nickel-chromium catalyst employed contained about 1 weight percent chromium based on the total weight of the catalyst.

From the foregoing, particularly with reference to Examples 1 to 4, it appears that the nickel-molybdenum catalysts of my invention having the highest activities contain from about 2.0 to 8.0 weight percent of molybdenum based on the tootal weight of the caatalyst, and that such a catalyst coontaining about 5 weight percent of molybdenum has particularly useful properties.

It will be apparent upon comparison of Examples 1 to 4 with Examples 6 to 8 that the nickel-molybdenum catalysts are equal if not superior to the nickel-chromium catalysts with regard to activity and further, as previously stated have the added advantages of having greater stability, better storing qualities and are easier to reproduce.

Although the foregoing examples have described only a few catalysts within the scope of the present invention, it will be apparent to those skilled in the art that other and specifically diflerent nickel-molybdenum catalysts from those specifically described may be employed with success in preparing catalysts of this invention. Furthermore, it is obvious that the digestion procedure employed 6 in preparing these catalysts from their corresponding alloys may be varied with respect to time, temperature, specific amounts of alloy treated concentration of leaching solutions and type of alkali used without departing from the broader aspects of the invention.

The catalysts of the present invention are useful in the hydrogenation of glucose to sorbitol as described and are also useful in many other catalytic reactions. Thus, these catalysts may be employed in the hydrogenation of other carbonyl-containing organic compounds to the corresponding hydroxy-containing compounds. They may also be employed in the hydrogenation of compounds containing aromatic unsaturation to form cycloaliphatic compounds. Similarly to other Raney-type nickel catalysts, these catalysts may be advantageously employed in certain dehydrogenation, dehalogenation and desulfurization reactions.

What 'I claim as new and desire to secure by Letters Patent of the United States is:

1. A catalyst for use in hydrogenation processes composed of a finely divided alloy consisting essentially of from about 0.25 to 12.0 weight percent molybdenum, and the balance substantially all nickel, said catalyst having been produced by dissolving aluminum from an aluminum-nic-kel-molybdenum alloy.

2. A catalyst for use in hydrogenation processes, composed of a finely divided alloy consisting essentially of from 2.0 to 8.0 weight percent molybdenum, and the balance substantially all nickel, said catalyst having been produced by dissolving aluminum from an aluminumnickel-molybdenum alloy.

3. A catalyst for use in hydrogenation processes, composed of a finely divided alloy consisting essentially of about 5.0 weight percent molybdenum, and the balance substantially all nickel, said catalyst having been produced by dissolving aluminum from an aluminum-nickel-molybdenum alloy.

4. The process for forming a finely divided, porous, catalyst for use in hydrogenation processes, comprising preparing an alloy consisting of essentially of from 0.25 to 12.0 weight percent molybdenum, from about 44 to 50 Weight percent nickel, and the balance substantially all aluminum, physically reducing the alloy to a finely divided state, and chemically dissolving the aluminum therefrom to form a porous catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 1,628,190 Raney May 10, 1927 1,915,473 Raney June 27, 1933 2,139,602 Raney Dec. 6, 1938 2,351,415 Farrell June 13, 1944 2,683,305 Goetzel July 13, 1954 2,750,271 Cucilleron et al June 12, 1956 OTHER REFERENCES Hansens Der Autbau der Zweistoffiegierungen, Berlin, 1936, PP- 910-911. 

1. A CATALYST FOR USE IN HYDROGENATION PROCESSES COMPOSED OF A FINELY DIVIDED ALLOY CONSISTING ESSENTIALLY OF FROM ABOUT 0.25 TO 12.0 WEIGHT PERCENT MOLYBDENUM, AND THE BALANCE SUBSTANTIALLY ALL NICKEL, SAID CATALYST HAVING BEEN PRODUCED BY DISSOLVING ALUMINUM FROM AN ALUMINUM-NICKEL-MOLYBDENUM ALLOY. 